REUTERSArmed men patrol as a man holds a Soviet Navy flag in the centre of the Crimean city of Simferopol March 1, 2014.

KIEV (Reuters) - Ukraine launched a treason case on Sunday against the head of the navy, who surrendered his headquarters on Sunday in the Crimean port of Sevastopol on only his second day on the job.

Denis Berezovsky was shown on Russian television swearing allegiance to the pro-Russian regional leaders of Crimea. Russian forces have seized the Black Sea peninsula and told Ukrainian forces there to give up their weapons.

"During the blockade by Russian forces of the central headquarters of the navy, he declined to offer resistance and laid down his weapons," said Viktoria Syumar, deputy secretary of Ukraine's Security Council.

"The prosecutor's office has opened a criminal case against Denis Berezovsky under statute 111: state treason," she said. Another admiral, Serhiy Hayduk, was placed in charge of the navy.